Personally I feel in lower level content you should simply do your best to hold aggro and if a DPS pulls for you or the rip aggro off try to get it back but if you do not do not worry. The mobs in Halatali, Sas etc. . . do not hit all that hard so other players can easily take one or two without much sorry. Do not bother to fight them group if they desire a quicker paced run. Either adjust or leave said group. While it might be rough when you run into a group that tries to speed run when you are either unwilling or not capable of doing so yet. Remember it is a group game and you are simply one part of the group, if the majority of the group desire such a run make the choice to adjust or leave but never be vindictive about it. Of course communication is key and if you tell a group before hand that you wish for a full clear or that you are new most people will be understanding.

Though same goes for a lone player that wishes to force larger pulls or tries to speed the group up. If the rest of the group is fine with a slower paced run or full clear kindly ask them to stop if they do not do let said player do their own thing until you can vote kick.